package tomo

import "errors"
import "git.tebibyte.media/sashakoshka/tomo/data"
import "git.tebibyte.media/sashakoshka/tomo/elements"

var backend Backend

// Run initializes a backend, calls the callback function, and begins the event
// loop in that order. This function does not return until Stop() is called, or
// the backend experiences a fatal error.
func Run (callback func ()) (err error) {
	backend, err = instantiateBackend()
	if callback != nil { callback() }
	err = backend.Run()
	backend = nil
	return
}

// Stop gracefully stops the event loop and shuts the backend down. Call this
// before closing your application.
func Stop () {
	if backend != nil { backend.Stop() }
}

// Do executes the specified callback within the main thread as soon as
// possible. This function can be safely called from other threads.
func Do (callback func ()) {
	if backend == nil { panic("no backend is running") }
	backend.Do(callback)
}

// NewWindow creates a new window using the current backend, and returns it as a
// Window. If the window could not be created, an error is returned explaining
// why. If this function is called without a running backend, an error is
// returned as well.
func NewWindow (width, height int) (window elements.Window, err error) {
	if backend == nil {
		err = errors.New("no backend is running.")
		return
	}
	return backend.NewWindow(width, height)
}

// Copy puts data into the clipboard.
func Copy (data data.Data) {
	if backend == nil { panic("no backend is running") }
	backend.Copy(data)
}

// Paste returns the data currently in the clipboard. This method may
// return nil.
func Paste (accept []data.Mime) (data.Data) {
	if backend == nil { panic("no backend is running") }
	return backend.Paste(accept)
}